Because people are irrational and clickbait runs rampant.
If they contract testing of the beta to a 3rd party, they don't want them running benchmarks because if they get released, news organizations will jump on it, broadcasting the performance hit.
This matters because when later beta versions improve performance, the news about the improved performance doesn't spread nearly as much. Even if it does, the first impression sticks, and there's nothing Intel will be able to do about it.
Amazing how many people are still doing mental gymnastics to give Intel the benefit of the doubt. This should have stopped being the default position a while ago.
If they contract testing of the beta to a 3rd party, they don't want them running benchmarks because if they get released, news organizations will jump on it, broadcasting the performance hit.
This matters because when later beta versions improve performance, the news about the improved performance doesn't spread nearly as much. Even if it does, the first impression sticks, and there's nothing Intel will be able to do about it.